1. Field of the Invention
This invention relates to shock suppressors and, more particularly, to a velocity sensitive mechanical snubber.
2. Description of the Prior Art
In many applications there is a need to restrain, minimize or suppress the movement of equipment and piping, relative to its supporting enclosure, resulting from disturbing forces such as flow pulsation, sway, pipe rupture thrust and seismic movement. This restraint or shock suppression, moreover, must be provided during disturbances of high velocity movement or acceleration whereas, during normal thermal movement, expansion or contraction, the low velocity movement associated therewith must be permitted.
More specifically in commercial power generating plants there is a need for shock suppressors which when subjected to disturbing forces of a predetermined minimum level, will act as a stiff strut or support to prevent relative movement between the equipment or piping attached thereto and the building or power plant structure. For example, from a safety viewpoint it is desirable to prevent a ruptured pipe from whipping about the interior of the power plant building. Furthermore, in order to readily calculate the safe design of a nuclear power plant subject to seismic disturbances, it is also desirable to fixedly connect the equipment and piping within the power plant building to the building structure to prevent relative motion between the moving building and the equipment therein. In addition, because of the large structures and temperatures involved in commercial power plants thermal expansion and contraction on the order of several inches may result. In view of the disturbing forces which may act upon the equipment and piping within the power plant and the thermal movements associated with the operation of the power plant a shock suppressor or restraint which will serve as a stiff high spring rate strut in response to a high reaction velocity movement and which will also serve to allow thermal movement is believed to be necessary.
Shock suppressors or dampers generally encompass hydraulic-piston type dampers, spring dampers and mechanical i.e., frictional, suppressors. More particularly, the mechanical suppressors generally comprise a linearly moving portion coupled to spring and rotating friction portions which provide the mechanical restraint. All of the above devices, moreover, generally consist of reservoirs and valves, or screwnut assemblies, centering springs and friction plates and are usually elaborate, expensive, high tolerance structures difficult to repair assemble and inspect, some even having orientation restrictions.
Accordingly, there is a need to provide a rugged shock suppressor which acts as a rigid strut with a high overall spring rate capable of resisting an externally imposed disturbance while permitting relatively low velocity movement such as thermal expansion and contraction and which is also simple and economical (low tolerance) in design, easy to inspect and assemble and is not orientation restricted.